1. Field of the Invention
The present invention relates to reactors that can be used for vehicles such as electric vehicles and hybrid vehicles and in environments subject to temperature changes.
2. Description of the Related Art
Reactors are passive elements that use a winding that introduces inductive reactance into an alternative component. A reactor includes a main body and a supporting member that secures the main body.
The main body of the reactor has a core, a resin mold, and a coil. The core is mainly made of a magnetic material. The core is enclosed in the resin mold and then the coil is wound on the outer surface of the resin mold. The support member is for example a bathtub shaped metal case that encloses the main body and also functions as a heat sink base.
Since such a reactor is composed of a main body enclosed in a resin enclosure and a case mainly made of a metal, it is necessary to consider the different linear expansion coefficients of resin and metal. In the past, a retainer was located on the upper surface of a resin mold and the resin mold was held by both the case and the retainer such that the main body was secured to the case (refer to for example JP2004-241475A and JP2008-147566A). A cushion rubber was located between the retainer and the upper surface of the resin mold so as to prevent the retainer from breaking the resin mold.
Since the cushion rubber absorbed a gap change that occurred between the main body and the case due to a heat change, the resin mold and the cushion rubber slid over the cushion rubber and thereby no stresses were imposed on each constituent member.
Although the structure in which the main body of the reactor is held by the retainer and the case is effective if the reactor is directly secured to the case. However, some reactors may have a structure in which the main body is not directly secured to the case, but through a plurality of fasteners. In this case, the main body is not held by the retainer and the case.
Thus, in such reactors, a gap change that occurs between the main body and the case due to different linear expansion coefficients causes a tensile stress and a compression stress to be imposed on the fasteners. The reactions against these stresses may break the main body and the case.
Next, another related art reference will be described. A resin mold of a reactor according to another related art reference has a plurality of metal fasteners that protrude from its periphery. The main body of the reactor is secured to the supporting member through the metal fasteners using bolts.
Generally, the metal fasteners are set as inserts in a die of the resin mold. The die is filled with a resin. As a result, the metal fasteners are formed integrally with the resin mold. In other words, one end of each of the metal fasteners is buried in the resin of the resin mold and the other end thereof is exposed therefrom (refer to for example JP2012-114190A, JP2009-272508A, and JP2009-026952A).
In recent years, vehicles such as electric vehicles and hybrid vehicles that use motors as drive sources have been rapidly developed. Thus, it has been concerned about whether or not reactors can withstand in environments where they are subject to large vibrations has been concerned as one of interests. Thus, the reactors need to have an improved robustness against vibrations propagated from the external environments.
A measurement result of the distribution of stresses imposed on ordinary reactors reveals that large stress concentrations occur at the bases of metal fasteners and at the boundaries of the bases of the fasteners and the resin mold. If a large external impact load is imposed at an ordinary reactor, it is likely that cracks occur at the boundaries of the bases of the fasteners and the resin mold and result in breaking the reactor.